This invention is directed to improvements in a load bearing fluid cushion vehicle of the general type disclosed in my U.S. Pat. No. 3,768,588 issued Oct. 30, 1973, entitled "Structure to Form a Load Bearing Air Cushion for a Vehicle", which patent is hereby incorporated into the present disclosure by reference.
U.S. Pat. No. 3,768,588 discribes a load bearing apparatus for a fluid cushion vehicle which is capable of containing a lifting fluid cushion between the underside of the vehicle and the surface over which the vehicle is operated. This apparatus is characterized by an annular seal assembly which encompasses and contains the lifting fluid cushion. This annular seal assembly includes an upper inflatable hanger envelope and a lower flexible seal. U.S. Pat. No. 3,768,588 teaches that it is advantageous to place the inflatable hanger envelope in series with the fluid cushion cavity so that the hanger envelope is inflated from the fluid cushion. However, experience has shown that undesirable dynamic interactions between these series-connected cavities may occur under some conditions. The present invention describes means for retaining the advantages of inflating the hanger envelope automatically from the fluid cushion while effectively providing dynamic isolation between the fluid cushion and the hanger envelope.
A second problem occurs in fluid cushion vehicles constructed in accordance with the teachings of U.S. Pat. No. 3,768,588, if they employ four or more lifting fluid cushions to support the vehicle. In such vehicles, if all lifting cushions operate independent of each other, a statically indeteriminant condition can develop in which fluid cushions located under diagonally opposite corners of the vehicle attempt to support the total weight of the vehicle while the other fluid cushions fail to pressurize sufficiently to carry their share of the load. This problem is solved in the present invention by interconnecting the inflatable hanger envelopes of the fluid cushions in such a manner as to produce only three independent sets or groups of fluid cushions. These three groups of fluid cushions then pressurize equally and share the total weight of the vehicle in a statically determinant manner.